China has experienced a substantial increase in HIV and STD infection in the past two decades. Sexual transmission of HIV from current high-risk groups such as IV drug users, prostitutes, and paid blood donors, to the general population, is increasing in frequency. One of the most serious HIV/STD challenges that China faces is mounting an effective HIV/STD prevention intervention effort to target the vulnerable 100 million rural-to-urban migrants. While there has been growing interest to devise effective, affordable and culturally appropriate prevention strategies, to date there is no systematic HIV/STD prevention effort targeting migrants in China. We propose this 5-year study to test two intervention approaches (i.e., behavioral intervention and voluntary counseling and testing) in a three-cell randomized controlled efficacy trial among young rural-to-urban migrants (15 through 24 years of age) in two major cities (Nanjing and Beijing) in China. Applying the methodology that has been used by the "Focus on Kids" research team in the U.S., Namibia, Viet Nam and China, this proposed study has three primary aims: (1) conduct a formative study on HIV/STD risk perception and risk behaviors among male and female rural-to-urban migrants aged 15 to 24 years in China; (2) adapt, implement, and evaluate a social cognitive theory-based HIV risk reduction behavioral intervention targeting rural-to-urban migrants by applying the methodology that has been used by the "Focus on Kids" research team in the U.S., Namibia, Viet Nam and China; (3) adapt, implement, and evaluate a voluntary counseling and testing (VCT) intervention program by modeling a "state of the art" counseling program developed by the CDC Project RESPECT. The secondary aims include: (1) develop and test effective recruitment and retention strategies in reaching the migrant populations; (2) expand and train a local HIV prevention/research network who will maintain/enhance research capacity in HIV/STD prevention targeting migrants in China; and (3) develop an intervention package, including materials and practical recommendations, to guide future study and dissemination of the program. The proposed study is an interdisciplinary international collaboration between the West Virginia University School of Medicine and the China National Center for STD Control and two major research institutes (Nanjing University and Beijing Normal University) in China.